The objective of these studies is to examine forebrain influences on respiratory and cardiovascular activity as a function of sleep-waking state, using long-term recording of single neurons in defined areas of the forebrain, pons and medulla. Neuronal discharge in these areas will be studied in relation to timing and degree of activation of diaphragmatic and upper airway muscles and to cardiovascular parameters. The cardiovascular relationships that will be studied include neuronal discharge correlations with 1) transient blood pressure rise and fall, 2) changes in cardiac cycle rate and variability associated with sleep states, and 3) blood pressure manipulation within these states. These studies will primarily utilize intact drug-free cats, but tracheotomized, vagotomized preparations will be used for certain tests. For simultaneous recording of neurons during sleep and waking states, microelectrodes will be placed in the orbital frontal cortex and central nucleus of the amygdala in the forebrain, and in brain stem areas associated with respiratory and cardiac control--including the hypoglossal nucleus, nucleus ambiguus, nucleus tractus solitarius and parabrachial pons. Electrodes will be inserted for recording EMG activity from the diaphragm, genioglossi muscles of the tongue and laryngeal dilator muscles. Catheters will be positioned for recording venous and arterial pressure. Experimental variables will include 1) different sleep-waking states, 2) transient elevation of blood pressure by means of phenylephrine administration, balloon inflation in the aorta and electrical stimulation of the central nucleus of the amygdala, 3) hypercapnic and hypoxic challenges in intact and vagotomized preparations, 4) tracheal occlusion, and 5) electrical stimulation of forebrain and pontine sites. Discharge relationships between forebrain and brain stem areas will be examined using cross-correlation procedures and selective analysis of inter-network versus intra-network spike dependencies. The relationship between neuronal discharge and electromyographic activity of respiratory musculature will be examined using pre-post stimulus time histograms and time series analysis techniques. Histological assessment will include localization of the electrode tip as well as immunocytochemical examination of neurons in the vicinity of the electrode tip site.